Update Demo with HttpClient (Azure#34680)

Author: rajkumar-rangaraj

sdk/monitor/Azure.Monitor.OpenTelemetry/tests/Azure.Monitor.OpenTelemetry.Demo/Program.cs

@@ -3,6 +3,7 @@
 
 #if NET6_0_OR_GREATER
 using System.Diagnostics;
+using System.Net.Http;
 using Azure.Monitor.OpenTelemetry;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.Extensions.Logging;
@@ -31,6 +32,10 @@
 app.MapGet("/", () =>
 {
     app.Logger.LogInformation("Hello World!");
+
+    using var client = new HttpClient();
+    var response = client.GetAsync("https://www.bing.com/").Result;
+
     return $"Hello World! OpenTelemetry Trace: {Activity.Current?.Id}";
 });